Exam 1 - Capnography Flashcards
What are some effects of Hypercarbia? Select 3
A. K+ shifts from intracellular to intravascular
B. increases cerebral blood flow
C. increases PVR
D. decreases ICP
E. decreases PVR
A. Potassium shifts from intracellular to intravascular
B. Increases cerebral blood flow (CBF) which… Increases ICP in susceptible patients
C. Increases pulmonary vascular resistance (b/c of vasoconstriction)
and also, Respiratory acidosis can develop over time
Some effects of Hypocarbia include: select 3
A. decreased ICP
B. increased PVR
C. K+ shifts from intracellular to intravascular
D. blunts normal drive to breathe
E. vasodilation
A. Decreases CBF, which decreases ICP
D. Blunts normal urge to breathe
E. Decreases pulmonary vascular resistance, b/c of vasodilation
Also:
Potassium shifts into the intracellular space (serum K decreases)
and could also cause Respiratory alkalosis
Capnography provides information primarily on ventilation but can give info on:
A. pulm blood flow
B. integrity of breathing circuit
C. estimation of adequacy of CO
D. all of the above
E. only A and B
D. all of the above
* Integrity of breathing circuit
* Estimates the adequacy of cardiac output
* Pulmonary blood flow
and:
* Aerobic metabolism
* Placement of ETT/LMA (presence of ETCO2)
The Bohr equation calculates:
A. alveolar dead space
B. physiologic dead spce
C. anatomic dead space
D. airway dead space
B. Physiologic dead space (airway ds + alveolar ds)
What makes up anatomical dead space? select 2.
A. respiratory zone
B. conducting zone
C. nose, trachea, bronchi
D. alveoli not partaking in gas exchange
B. conducting zones of the airway
C. nose, trachea, bronchi
normal ADS = 150 mL
The portion of physiologic dead space that does not take part in gas exchange but is within the alveolar space is called:
A. airway DS
B. anatomic DS
C. alveolar DS
D. physiologic DS
C. alveolar dead space
Some conditions that increase alveolar dead space (V/Q mismatching) include: select 2.
A. underinflation of alveoli
B. pulmonary hypertension
C. hypovolemia
D. pulmonary embolus
C. Hypovolemia
D. Pulmonary embolus
and:
* Pulmonary hypotension
* Ventilation of nonvascular airspace
* Obstruction of precapillary pulmonary vessels
* Obstruction of the pulmonary circulation by external forces
* Overdistension of the alveoli
What is the best method to confirm endotracheal intubation?
A. breath sounds
B. capnometry
C. capnography
D. CXR
C. capnography
detection of CO2 breath by breath
Time capnography is a pressure vs time plot for ETCO2 waveform. What is the difference between high-speed vs slow-speed?
A. high-speed can show info about each breath while slow-speed shows more of a trend
B. slow-speed shows info about each breath while high-speed shows more of a trend
C. there is no difference between the two
A.
* High-speed – user can interpret information about each breath
* Slow-speed – appreciation of the expired and inspired trend
What is the most common gas sampling system?
A. mainstream
B. side-stream
C. flow-over
D. blow-by
B. Side-stream gas analyzer (downside: there’s a transport and rise time delay!)
What phase on a capnograph will an ETCO2 be measured at?
at end-point of phase 3.
What can increase ETCO2? select 3.
A. seizures
B. hypothermia
C. cardiac arrest
D. MH
E. thyrotoxicosis
F. pulmonary embolism
A. sz
D. MH
E. thyrotoxicosis
What can cause decreased ETCO2? select 3.
A. sepsis
B. fever
C. hyperventilation
D. hypotension
E. leak around ET cuff
F. rebreathing
C. hyperventilation
D. hypotension
E. leak around ET cuff
Difference between PaCO2 and ETCO2 is approx ____ mmHg.
5 mmHg
Ex: ETCO2 of 35 mm Hg = PaCO2 of approx. 40 mm Hg
so normal A-a difference is 5 mmHg
What are some V/Q mismatching problems that would increase the difference (aka widen the gap) between PaCO2 and ETCO2? Select 3.
A. MH
B. seizures
C. endobronchial intubation
D. aging
E. pulmonary embolism
F. hyperventilation
C. endobronchial intubation
D. aging
E. PE
- also, breathing patterns that fail to deliver alveolar gas at the sampling site (like COPD, neonates/infants, bronchospasm), increases the difference between PACO2 and true ETCO2 (alveolar gas)!
Fill in the blank:
CO2 measurement most commonly relies on infrared light absorption techniques. The __ the CO2 in the sample, the less IR light that reaches the detector.
A. greater
B. less
C. unchanged
A. The greater the CO2 in the sample, the less IR light that reaches the detector
What are the inspiratory and expiratory segments of a normal capnograph?
- Inspiratory – Phase 0
- Expiratory – Phases I, II, and III
Describe Phase I of a normal capnograph: select 2
A. alveolar plateau
B. no CO2
C. first expiratory upstroke
D. exhalation of anatomic DS
B. Essentially no CO2
D. Exhalation of anatomic dead space and the apparatus dead space (ETT, LMA)
phase 1 = baseline!
Describe Phase II of a normal capnograph.
- Expiratory upstroke begins (CO2-rich alveolar gas)
- Sampling of alveolar gases
- Normally steep uprise
Describe Phase III of a normal capnograph.
- Alveolar Plateau phase
- Normally representative of CO2 in alveolus
- Can be representative of ventilation heterogeneity, slightly increasing slope
Describe Phase 0 of a normal capnograph.
- Sometimes called phase IV
- Inspiration of fresh gas, remaining CO2 washed out
- Downstroke returns to baseline
Describe the Occasional Phase IV (Phase IV’) of a capnograph: select 2
A. sharp upstroke in PCO2 at the very end of phase II
B. inspiration of fresh gas
C. from closure of lung units with lower PCO2
D. remaining CO2 being washed out
E. seen in pregnant and obese patients
C. Upstroke probably results from the closure of lung units with lower PCO2 … Allows for regions w/ higher CO2 to contribute to more of the exhaled gas sample
E. Seen in pregnant and obese pts (decreased FRC and lung capacity)
* sharp upstroke in PCO2 at the very end of phase III
* Decreased FRC and lung capacity
The alpha angle of the capnograph increases with:
A. inspiratory airflow obstruction
B. rebreathing
C. expiratory airflow obstruction
D. low Vt with rapid RR
C. Angle increases with an expiratory airflow obstruction such as COPD, bronchospasm, or kinked ETT
alpha angle defined as:
* Separates phase II and phase III
* 100 – 110 degrees
The beta angle of the capnograph increases with:
A. rebreathing
B. malfunctioning inspiratory unidirectional valves
C. low Vt with rapid RR like with neonates
D. All of the above
E. All but B
D. all of the above- angle increases with malfunctioning inspiratory unidirectional valves, rebreathing, and low tidal volume with rapid respiratory rate (like w/ neonates)
Beta angle defined as:
- Separates phase III and phase 0; and 90 degrees
Describe the capnograph
- Normal Capnograph
- Mechanical Ventilation
Describe the capnograph
- Normal Capnograph
- Spontaneous Ventilation
What is the issue with this capnograph?
- Inadequate Seal around ETT
What is causing this capnograph?
- Faulty Inspiratory Valve (top capnograph)
- Rebreathing (bottom capnograph)
What is causing this capnograph?
- Sample line leak
Take note that this a small wave form and that ETCO2 does not even reach 40 mmHg
What is causing this capnograph?
- Hyperventilation
- Gradually decreasing waveforms
What is causing this capnograph?
- Hypoventilation
- Gradually increasing waveforms
What is causing this capnograph?
- Airway obstruction
What is causing this capnograph?
- Cardiac oscillation
- Often seen in pediatric patients, the heart is close to the trachea
What is causing this capnograph?
- Re-breathing soda lime exhaustion
Take note that rebreathing is occurring. The capnograph does not return to baseline.
What is causing this capnograph?
- NMBD’s wearing off
- Presence of a “curare cleft”
What is causing this capnograph?
- Over-breathing
- Notice the spontaneous breath between the mechanical breath
What is causing this capnograph?
- Esophageal intubation
